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The mkiv Supra Owners Club

Twin sequential twins?


tbourner

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Discussing with a workmate the options for a new Rover V8 he's just aquired, he's got several already and has built a Model A hot rod etc.

 

He said we should get a chassis (maybe from a scrap Audi Quattro), bodge fit (the rodders way) the V8 and have interchangeable shells for it - probably won't be road legal but fun none the less.

Then I showed him the Heffner Viper twin turbos and said we should put tubbies on it.

 

 

 

THEN we got talking about lag on twins on a V8, due to having 1 per bank. So I wondered what the problems would be of having a twin sequential system on each bank?

I'd gues you'd get issues with different boost from each side of the engine, so it'd be a bit lumpy with half the engine running 1.1bar and the other 0.9!!!

How about having the turbo outlet from one bank going round to the other side? So if one row produces more power, it produces more exhaust, so produces more boost for the other row?

 

It sounded like a good idea on paper, but I'm far too stupid to understand the pitfalls, and my mates classing me as the turbo expert at the moment! :faint:

 

:help:

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With the newer design turbo's out there, it shouldnt be that hard just to go with a twin setup. say its a 3.5 V8 rover. You looking at a 1.7L displacement for each bank. Now say tou run something like a gt28rs on each bank, thats a very very quick spooling turbo which is ideal for the 2.0l class and will push 58lb's of air

If an engine like the vg30dett found in the 300zx can get away with a tiny t22 garrett per bank (1.5L and 3 cylinders) and still make a healthy 280bhp at 9psi Then IMHO a rover V8 with 2 x gt28rs on 16psi should be a good combination without the Lag factor as they are a very very quick spooling turbo

 

At this point i will also add i dont know much about the engine characteristcs of the rover v8 lol

 

Marty

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How about having the turbo outlet from one bank going round to the other side? So if one row produces more power, it produces more exhaust, so produces more boost for the other row?

 

 

The Lotus Esprit 3.5 litre twin turbo V8 does this, but there is a balance pipe between the two plenum chambers as well.

 

Not sure that it immediately follows that a V engine has to have laggy turbos. Surely its a better setup to run two smaller turbos that spin up faster? Unless you want to have two really, really big turbos :)

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The Rover V8 is a big lazy lump. It's very old skool but that's very refreshing after dealing with these fangled 2JZ's ;)

 

Two small turbos should do the trick. Minimal lag and you won't suffer with power loss and boost tailoff up high as there isn't all that "up high" with the Rover V8 anyway. Which is another reason why you don't want big turbos, there isn't the rev range to deal with them. The cylinder heads are real blockers, 7000rpm is about the highest you can go as NA, so with forced induction it'd probably be even more strangled. Higher revs require expensive valvetrain stuff anyway.

 

Go for the 3.9 EFI if you can. For a turbo application you need EFI and a lot of 3.9's came with it, although if you were serious you'd junk the ECU and the MAF and use just the sensors, with bigger injectors and a standalone ECU to control a MAP based setup. If you've got a 3.5, consider changing the guts to 3.9, it apparently is the #1 thing to do for performance and drivability.

 

So two small turbos with a balancer pipe between the manifolds, and a blend pipe on the exhaust. Rev to 5500rpm, 6000rpm max, and enjoy the stump-pulling torque you'll get. Don't expect Supra-like power outputs though, pushing 300bhp will be an acheivement (bless 'em ;) ) Of course, it'll muffle the glorious V8 noise :( but that's a small price I guess.

 

-Ian

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